utils_test.libvirt: Make sure XML file has been created for create_disk_xml.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Support multiple disks and scsi disks for attach_disks.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Support to attach devices with --config.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Support format for creating disks.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Update logic of generating disks index.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
libvirt_xml.controller: Add controller relative operations.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Support multifunction of controllers for massive disks.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Merge pull request #1811 from yumingfei/scsi_enhancements

utils_test.libvirt: Scsi enhancements